1. Field of the Invention
The present invention relates to digital indication type speedometers, and particularly to improvements in a digital indication type speedometer comprising a speed counter for counting speed pulses emitted in proportion to a vehicle speed for a given gate time, an indication register for latching a value to be indicated commensurate to an output from said speed counter and an indicator for indicating the value latched in said indication register.
2. Description of the Prior Art
In general, a digital indication type speedometer for digitally indicating a running speed of a vehicle or the like comprises a speed counter for counting speed pulses emitted in proportion to a vehicle speed through the rotation of a propeller shaft, wheel or the like for a given gate time, an indication register for latching the preceding value counted by the speed counter while the speed counter is counting, and an indicator for indicating the value latched in the indication register. This digital indication type speedometer has such a characteristic feature that the vehicle speed is constantly digitally indicated by the indicator. However, with this speedometer, heretofore, an output of the speed counter has been directly latched in the indication registor as a value to be indicated, which is repeatedly indicated by the indicator, thereby a rewriting cycle of an indication is limited to substantially each given gate time, and the change in indication is slow during acceleration or deceleration, thus presenting a feeling of incompatibility between the degree of acceleration or deceleration and the change in indication. Whereas, during running at a constant speed, the change in indication is frequently made in accordance with slight changes in the vehicle speed as if it flickers, thereby deteriorating easiness in reading. More specifically, during running at a value between 59 km/h and 60 km/h for example, both of 59 km/h and 60 km/h are alternately indicated. This reaches its worst condition when an intermediate speed between 59 km/h and 60 km/h is set in a cruising speed control device of the vehicle. The shorter the gate time is, the more intense the flickering changes in indication become. Therefore, as a remedy for it, it has been taken into account to extend the gate time. However, if the response during acceleration or deceleration is taken into consideration, there is a limit in extending the gate time. Consequently, heretofore, there has been selected an intermediate value of a gate time in consideration of both factors as described above. However, the value thus selected could satisfy neither the condition during acceleration or deceleration, nor the condition during running at a constant speed.
In order to obviate the disadvantages as described above, it has been considered to change the gate time and the rewriting cycle of indication in accordance with the running conditions of the vehicle. However, the abovedescribed arrangement not only requires an acceleration sensor for sensing the running condition of the vehicle but also makes the after-treatment of signals be complicated, so that the abovedescribed arrangement is not practicable.